Extremely miniaturised motors based on electromechanical materials are able to make controlled fine positioning using only a relatively small amount of electrical power. Consumer products have often needs for extremely small, low weight, low power consumption and inexpensive motors.
In the U.S. Pat. No. 6,437,485, an electromechanical actuator based on a double electromechanical element is disclosed. The electromechanical element mechanically supports against a stator at respective outer ends. A driving portion is attached essentially at the middle of the electromechanical element and serves as the contact against a surface of a body that is intended to be moved. By supplying well-defined voltage signals to the electromechanically active portions of the electromechanical element, the driving portion is forced to move in two dimensions for transferring a motion to the body to be moved. The basic concept has proven to be very successful and further improvements have been disclosed e.g. in U.S. Pat. No. 6,747,394.
In the published international patent application WO 2004/088831 A1, resonance behaviours have been discussed. One embodiment was a motor of the type described above. Here it was stated that the operation was favoured e.g. by designing and arranging the electromechanical element in the motor such a way that two flexural resonance frequencies were situated relatively close in frequency relative each other.
In a practical motor manufacturing, it has been shown to be relatively impractical to verify the resonance frequencies during actual operation and even more impractical to try to modify the assembled arrangement if the resonance frequencies are not present at the intended values.